In the prior art there has been a need for antenna systems having substantially uniform and highly efficient electrical transmission characteristics, and more particularly a need for constant beam width patterns at substantially any frequency of operation of the antenna system. There are presently two main types of antennas that are somewhat frequency independent. These systems utilize two types of antennas: log periodic and spiral antennas. Spiral antennas do provide constant beam width patterns over wide frequency ranges of operation, but spiral antennas suffer certain shortcomings. This type of antenna can only operate at low power levels, has low efficiency, and exhibits wide beam width patterns that result in a lack of directivity and low antenna gain. Log periodic antennas are an improvement over spiral type antennas and have increased directivity due to somewhat narrower beam width patterns and this results in a medium gain antenna. However, log periodic type antennas can only handle medium power levels and have a beam width pattern that varies with frequency to a degree that is unacceptable in some applications. In addition, log periodic antennas do not function well above an operating frequency of 12 gigahertz.
To improve upon the characteristics of spiral antennas and log periodic antennas, conventional reflectors have been used therewith which are well known in the art. The spiral type antenna coupled with a reflector causes pattern beam width to be narrowed somewhat resulting in improved directivity and higher gain, but this combination still results in low power handling capability and low efficiency due to the limitation of the spiral antenna illuminating the reflector.
The combination of log periodic type antennas with conventional reflectors also results in narrower beam width patterns giving increased directivity hence higher gain, but this combination can only operate at medium power levels and still cannot operate above 12 gigahertz due to the limitation of the log periodic type antenna illuminating the reflector. In addition, the pattern beam width of a log periodic type antenna varies somewhat with frequency. The factor combined with the shift in phase center along the length of a log periodic type antenna with changing frequency, causes pattern disruptions that are often unacceptable.
Although there are improvements in some antenna system electrical characteristics in combining a conventional reflector with either a spiral type antenna or a log periodic type antenna there is no longer a constant pattern beam width over large frequency ranges of operation.
Accordingly, there is a need in the art for a new antenna reflector that gives constant beam width patterns over wide frequency ranges of operation of an antenna while providing high directivity and gain, with power handling capability and efficiency determined solely by the feed antenna illuminating the reflector.